/* ==========================================
 * JGraphT : a free Java graph-theory library
 * ==========================================
 *
 * Project Info:  http://jgrapht.sourceforge.net/
 * Project Creator:  Barak Naveh (http://sourceforge.net/users/barak_naveh)
 *
 * (C) Copyright 2003-2008, by Barak Naveh and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */
/* -----------------
 * DefaultGraphMapping.java
 * -----------------
 * (C) Copyright 2005-2008, by Assaf Lehr and Contributors.
 *
 * Original Author:  Assaf Lehr
 * Contributor(s):   -
 *
 * $Id: DefaultGraphMapping.java 1258 2013-04-18 20:27:18Z freecode4susant $
 *
 * Changes
 * -------
 */

package org.jgrapht.graph;

import org.jgrapht.Graph;
import org.jgrapht.GraphMapping;

import java.util.Map;

/**
 * Implementation of the GraphMapping interface. The performance of <code>
 * getVertex/EdgeCorrespondence</code> is based on the performance of the
 * concrete Map class which is passed in the constructor. For example, using
 * hashmaps will provide O(1) performence.
 *
 * @author Assaf
 * @since Jul 30, 2005
 * @param <V>
 * @param <E>
 */
public class DefaultGraphMapping<V, E> implements GraphMapping<V, E> {

    private final Map<V, V> graphMappingForward;
    private final Map<V, V> graphMappingReverse;
    private final Graph<V, E> graph1;
    private final Graph<V, E> graph2;

    /**
     * The maps themselves are used. There is no defensive-copy. Assumption: The
     * key and value in the mappings are of valid graph objects. It is not
     * checked.
     *
     * @param g1ToG2
     * @param g2ToG1
     * @param g1
     * @param g2
     */
    public DefaultGraphMapping(final Map<V, V> g1ToG2, final Map<V, V> g2ToG1,
                               final Graph<V, E> g1, final Graph<V, E> g2) {

        this.graph1              = g1;
        this.graph2              = g2;
        this.graphMappingForward = g1ToG2;
        this.graphMappingReverse = g2ToG1;
    }

    public E getEdgeCorrespondence(final E currEdge, final boolean forward) {

        final Graph<V, E> sourceGraph;
        final Graph<V, E> targetGraph;

        if (forward) {

            sourceGraph = this.graph1;
            targetGraph = this.graph2;

        } else {

            sourceGraph = this.graph2;
            targetGraph = this.graph1;
        }

        final V mappedSourceVertex = getVertexCorrespondence(sourceGraph.getEdgeSource(currEdge),
                                         forward);
        final V mappedTargetVertex = getVertexCorrespondence(sourceGraph.getEdgeTarget(currEdge),
                                         forward);

        if ((mappedSourceVertex == null) || (mappedTargetVertex == null)) {
            return null;
        } else {
            return targetGraph.getEdge(mappedSourceVertex, mappedTargetVertex);
        }
    }

    public V getVertexCorrespondence(final V keyVertex, final boolean forward) {

        final Map<V, V> graphMapping;

        if (forward) {
            graphMapping = graphMappingForward;
        } else {
            graphMapping = graphMappingReverse;
        }

        return graphMapping.get(keyVertex);
    }
}

// End DefaultGraphMapping.java



